1. Field of the Invention
This invention relates generally to a method of making a composite copper or copper alloy material having incorporated therein second phase particles. More particularly, this invention relates to the method of making a composite copper alloy comprising having a copper or copper base alloy matrix having a second phase of ceramic particles dispersed therein.
2. Background Information
Copper and copper base alloy materials are useful in many applications. For some applications, it is desirable to modify the properties of copper or the copper base alloy material by the incorporation of ceramic particles therein to improve such properties as strength, wear resistance, hardness, modulus elasticity and thermal characteristics.
However, for such ceramic particles to be effective in improving the properties of the alloy, the interface between the matrix and the particles must be strong. That is, the ceramic particles must bond with the matrix material. In the case of copper, it has been found that under normal casting conditions, the ceramic particles do not bond to the copper matrix and accordingly, the resulting alloy does not realize improved properties.
One relatively new method of casting metal is the spray casting process which generally comprises the steps of atomizing a fine stream of molten metal, depositing the particles onto a collector where the hot particles solidify to form a preform and then working or directly machining the preform to generate the final shape and/or properties required.
One form of such a spray casting process is generally known as the OSPREY process and is more fully disclosed in U.S. Pat. Nos. RE 31,767 and 4,804,034 as well as United Kingdom Patent No. 2,172,900. Further details about the process are contained in the publication entitled "The Osprey Preform Process" by R. W. Evans, et al, Powder Metallurgy, Vol. 28, No. 1 (1985).
In the OSPREY process, a controlled stream of molten metal is poured into a gas-atomizing device where it is impacted by high-velocity jets of gas, usually nitrogen or argon. The resulting spray of metal particles is directed onto a "collector" where the hot particles re-coalesce to form a highly dense preform. The collector is fixed to a mechanism which is programmed to form a sequence of movements within the spray, so that the desired preform shape can be generated. The preform can then be further processed, normally by hot working, to form a semi-finished or finished product.
The OSPREY process has also been developed for producing strip or plate or spray-coated strip or plate as disclosed in U.S. Pat. No. 3,775,156 and European Patent Application No. 225,080. For producing these products, a substrate or collector such as a flat substrate or an endless belt is moved continuously through the spray to receive a deposit of uniform thickness across its width.